Cognitive Glioscience group has contributed to the field of gliotransmission by creating several seminal publications on the channel-mediated gammaAminobutyric acid (GABA) and glutamate release from astrocytes. They later identified the biosynthetic pathway for astrocyte GABA and found monoamine oxidase B to be the key enzyme for GABA production which raised the possibility that astrocytes can directly participate in cognitive processes via astrocytic GABA.
The group also found a connection with GABA and H2O2 from reactive astrocytes and impaired memory in mouse models of Alzheimer’s disease, leading them to propose astrocytic GABA- and H2O2-related pathways might be a diagnostic tool, biomarker, and therapeutic target for both neurological diseases Alzheimer’s and Parkinson’s. The research is notable as it revealed that astrocytes, like neurons, play a significant role in cognitive processes. The findings also resulted in a technology transfer to Neurobiogen which will be prepared for a phase I clinical trial in 2022.
Thus, the group continues to investigate the cognitive functions of 1) GABA synthesis and release from glia, 2) molecular mechanisms of glutamate and d-serine release from glia, 3) astrocytic volume transient and brain plasticity, and 4) reactive astrogliosis and neurodegeneration.
Astrocyte, Reactive astrocyte, Astrocyte neuron interaction, GABA, Glutmate, Dserine, ATP release, Metabolism, Synaptic transmission and plasticity, Memory, Alzheimer’s disease, Parkinson’s disease, Spinal cord injury, Depression, PTSD
Director C. Justin Lee
Our group has contributed to the field of gliotransmission (release and function of transmitters from glia) with seminal publications on the channel-mediated GABA and glutamate release from astrocytes. We demonstrated, for the first time, the channel-mediated release mechanism of the major inhibitory transmitter GABA from astrocytes in cerebellum involving Best1 channel and further demonstrated that the source of tonic inhibition in cerebellum is astrocytic GABA. We subsequently identified the biosynthetic pathway for GABA in astrocyte to be the putrescine degradation pathway leading to GABA production, in which the monoamine oxidase B (MAO-B) is the key enzyme for GABA production.
This series of studies implicates that astrocytes by tonically releasing the major inhibitory transmitter GABA, can exert strong inhibitory drive to the brain activity, raising a profound possibility that astrocytes can directly participate in cognitive processes via astrocytic GABA. Utilizing these newly identified molecular targets, Best1 and MAO-B, we further demonstrated that tonic GABA inhibition in cerebellum is critical for motor coordination.
In parallel, we have revealed the pathological role of astrocytic GABA, especially in Alzheimer’s disease (AD) and Parkinson’s disease (PD). We provide compelling pieces of evidence that hippocampal or SNpc astrocytes aberrantly produce GABA via MAO-B and release through Best1 channels in AD or PD, respectively. The aberrant GABA from astrocytes inhibits neighboring neuronal activity to impair memory in AD or to cause motor deficit in PD. We further propose that the astrocytic GABA could be an optimal biomarker, diagnostic tool, and therapeutic target for AD and PD. We continue to investigate the role of aberrant GABA from astrocytes in white matter stroke, recovery after spinal cord injury, obesity, and epilepsy.
In addition to GABA, we have investigated the molecular mechanism of glutamate release from astrocytes because glutamate has been known to be released from astrocytes but the release mechanism has been controversial. Glutamate is the major excitatory transmitter that enhances neuronal excitability.
Through an intense investigation, we have clearly demonstrated that glutamate is released in two models: fast mode through TREK-1 containing K2P channel and in slow mode through Best1 channel in hippocampal astrocytes. We have subsequently reported that Best1-mediated glutamate release contributes to receptor mediated synaptic plasticity in hippocampus upon activation of PAR1 (a Gq-coupled GPCR). Through this series of studies, we have demonstrated that astrocytic glutamate and GABA are the key modulator for excitation-inhibition balance (E/I balance) in the brain, which is mainly dependent on the levels of glutamate and GABA. In addition to glutamate, we found that Best1 is also capable of releasing d-serine, which can act as a co-agonist of NMDA receptors to participate in synaptic plasticity. We are actively investigating the possibility of astrocytes as the potential therapeutic target for various brain disorders such as schizophrenia, autism, ADHD, epilepsy, depression, and etc, which are known to be caused by impaired E/I balance.
We have also contributed to the field of glioscience by identifying and characterizing several astrocytic ion channels. We identified that astrocytic two-pore potassium channel K2P, which is responsible for passive conductance with a subunit composition of a heterodimer of TWIK-1 and TREK-1. We further proposed the heterodimer of TWIK-1 and TREK-1 as the potential therapeutic target of epilepsy, depression, and anxiety disorders caused by dysregulation of potassium ion concentration. Next, we found the identity of astrocytic volume-regulated anion channel (VRAC), which is tweety-homolog (Ttyh).
So far the identity of VRAC has been proposed to be LRRC8. However, we firstly demonstrated that the pore-forming subunit of VRAC in astrocytes is Ttyh, but not LRRC8. More importantly, we have demonstrated for the first time that astrocytic volume change through aquaporin-4 water channel is critical for synaptic plasticity and established the novel concept of volume plasticity in both mouse and human. We have demonstrated that this astrocytic volume change is critical for spatial memory in mouse and language-associated learning and memory in human. This ground-breaking finding and novel concept of astrocytic volume will be the basis for a paradigm shift in brain plasticity from the traditional view of neuroplasticity to the new concept of glioplasticity and memory.
During the course of delineating the molecular and cellular mechanisms of gliotransmission, we have encountered the important concept of reactive gliosis, which is often referred to as the basis for neuroinflammation.
Although pathologic contributions of reactive astrocytes have been implicated in AD and other neurodegenerative diseases, their in vivo functions have remained elusive due to the lack of an appropriate experimental model. We have recently developed an astrocyte-specific toxin receptor model, and found that the astrocytes, which have an active autophagy system, not only remained alive but selectively became reactive. Our study identifies the severe reactive astrocytes as a key determinant of neurodegeneration in AD. We anticipate that this novel mechanistic insights will be very useful for developing drug candidates for AD and other neurodegenerative diseases, such as PD, traumatic brain injury, stroke, and etc.
To realize the goals and visions of the Center for Cognitive Glioscience,
we will divide
the research areas based on the systemic level of research in terms of brain functions.
We have a lab meeting on Mon and a journal club on Fri from 9:00 AM. During this meeting we will discuss lab business and present your own data collected in the past week. Attendance for each meeting is required for all members, please be prompt.
Cleaning of your experimental environment is very important for your health as well as
quality of the experimental results. Therefore, we may ask you to clean up daily.
In every morning: Right after coming to lab, you may need to check the status of lab
bench.
Obtaining basic skills is essential for you to perform experiments properly.
You can find more protocols from the backup folder of our lab
ftp://203.247.189.127:4022 (Public NAS)Neural basis of perceptual awareness and statistical perception. We aim to better understand brain mechanisms of various perceptual, cognitive, and conscious processes by deploying multiple techniques ranging from behavioral methods such as psychophysics and eye tracking to brain imaging techniques such ECoG, EEG, and MRI. We also use machine learning techniques and bio-inspired computational modeling to probe the spatiotemporal pattern dynamics of brain imaging data and develop a mechanistic model of consciousness.
Cognitive neuroscience, Predictive coding, Statistical perception, Abstraction, General intelligence, Attention, Consciousness, Brain-imaging, Bio-inspired neural modeling
Our laboratory's primary goal is to develop non-invasive neural modulation algorithms that reliably enhance brain function over the long term. To achieve this, we utilize electrophysiology and in vivo imaging to understand brain signal transmission and network interactions, aiming to modulate neuroplasticity non-invasively in both normal brain function and models of brain disorders and neurological conditions.
The core of our research focuses on non-invasive ultrasonic neuromodulation. Our objective is to develop innovative ultrasonic neuromodulation techniques that modulate brain activity without surgical intervention, thereby enhancing brain function safely and effectively.
We are developing new non-invasive ultrasonic neuromodulation technologies for clinical applications while also exploring alternative treatments for neurological and psychiatric disorders. To this end, we employ various electrophysiological and behavioral analysis techniques, including Whole-Cell Patch Configuration, Brainwave (EEG) Recording, High-Resolution Fluorescence Microscopy, Optogenetics, and Behavioral Modeling of Impaired Sensorimotor Gating.
Our research aims to thoroughly understand the neural circuits and synaptic plasticity involved in learning and memory. These creative and challenging projects are expected to significantly contribute to the growth of young researchers and expand our academic influence both domestically and internationally.
Cognitive and behavioral neuroscience, Cellular and molecular neurophysiology, Learning and memory
Astrocyte, Astrocyte Maturation, Astrocyte Morphogenesis, Autism Spectrum Disorder (ASD), Reactive Astrocyte, Astrocyte-Neuron Interaction, GABA, Attachment Formation, Synaptic Transmission and Plasticity, Memory, Enteric Glia, Postpartum Depression
Computational neuroscience, NeuroAI, Cerebellum, Sensorimotor learning, Biophysical neural modeling, Network dynamics